I still get the same issue. I called my voicemail. It's set up and I was able to change my voicemail like that and listen to my messages, but the visual voicemail on my iPhone doesn't show any messages and will not allow me to create a new voicemail like it use to. Every time I click save it says "Greeting save failed. Failed to save your greeting"
Verizon only: Unfortunately, if you have set up the voicemail successfully but still unable to change the greetings of Voicemail from the Voicemail tab, then dial *86 and select option 4 to make a change. Step #1: Launch the “Phone” app on your iPhone. Step #2: Tap “Voicemail”. Step #3: Select “Greeting” on the upper-left corner of the screen. Step #4: In case, you are also using eSIM then select the second network to change voicemail greetings. Step #5: Select “Custom”. From here you can record a greeting. Step #6: Tap “Record”.

Accessing voicemail on an Android phone can be achieved by hitting and holding down the 1 key on the number pad until the system dials your 10-digit phone number, as seen in the screenshot.
However, some cellular service providers allow users to access and update their voicemail by calling their own numbers from working landlines or phones on other wireless networks, so users whose accounts include such an option and who have access to alternative service could keep the voicemail greetings updated even when their own mobile phones cannot connect to cellular or internet service.